net/iproute2: Add timeout information and timeout progress indicator

With this patch we will show the currently set dad_timeout value to the
user. The timeout progress will be shown using dots.

The idea is stolen from _wait_for_carrier() in init.d/net.lo.in.

This patch will also undo commit

  732a9a4999f479ee97a404252f6a0eba4a86e338

See bug 488250 for more information.
net/iproute2: No need to use grep for checking tentative state

We don't need grep to check the tentative state, because the 'ip' utility
has a builtin command for that.
_wait_for_carrier(): Workaround for output when using rc_parallel="YES" is no longer needed

_wait_for_carrier() was using a workaround when rc_parallel is enabled.
This caused the following broken output:

  https://bugs.gentoo.org/attachment.cgi?id=361054

This patch fixes bug 488256 by removing the workaround, because this
workaround isn't needed anymore.